The invention relates to a common rail-type fuel injection system for a multi-cylinder internal combustion engine with magnetic valve controlled direct-injection fuel injection valves with a fuel admission passage leading in each valve housing to a spring-loaded nozzle needle and including a control piston with an integral control valve by which the fuel admission passage can be closed. The valve housing includes a spring space with a spring engaging the nozzle needle so as to bias it onto a nozzle needle seat. A control space is disposed on the backside of the control piston which is exposed to system pressure and, adjacent the control space, there is a cooperating magnetic valve by which the control space can be placed in communication with a pressure relief passage whereby, at the same time, the fuel supply passage leading to the nozzle needle can be opened, the fuel supply passage being also in communication with the pressure relief passage by way of a throttled communication passage.
DE 196 12 738 A1 discloses such a common rail injection system with magnetic valve controlled fuel injection valves. Each injection valve includes a control piston cooperating with a spring-loaded nozzle needle by way of the spring space delimited by the control piston. The spring space is in communication with a drain line of the fuel injection valve.
Upon malfunctioning of the injection valve either by a defect in the magnetic valve or jamming of the control piston, there is a permanent high pressure connection to the fuel injection nozzle which can lead to serious engine damage.
U.S. Pat. No. 5,109,827 discloses a common rail fuel injection system for a multi-cylinder internal combustion engine with magnetic valve controlled direct-injecting fuel injection valves which include throttling arrangements that do not provide for a closing of the needle valves when the injection valves are malfunctioning.
It is the object of the present invention to provide a fuel injection valve for a direct fuel injection system of the common rail type which includes means whereby, in a simple manner, engine damage by the fuel injection system becomeing defective is prevented but, nevertheless, emergency operation of the engine is still possible.